The application relates to a device for automatically injecting an agent, having a receptacle for the agent, which receptacle, along with an injection needle connected to the latter, is displaceable in a housing for the purpose of inserting the injection needle, and having a syringe piston that is displaceable in the receptacle for the purpose of expelling the agent.
Devices of the type mentioned above, so-called autoinjectors, are known in many kinds of embodiments. In particular, they serve to administer medication that the patient in question himself injects. A problem of such autoinjectors that has until now been solved only unsatisfactorily consists in the fact that the patient, after the insertion of the injection needle initiated by himself, does not know how long the expelling of the medication lasts and when he can pull the injection needle out again. A possible solution to this problem consists in connecting to the syringe piston an indicator element visible from the outside. Since, however, the syringe piston already, before the expelling of the medication, covers the distance required for the insertion of the injection needle, an indicator element connected directly to the syringe piston could easily give rise to misinterpretations and/or could increase the structural length of the autoinjector in an undesirable manner.
It is therefore a task of the present invention to provide a device of the type mentioned above, in which device it can be unambiguously determined from the outside when the injection process has ended, and which has no significant effect on the structural length of the autoinjector.